Scientists Describe Asteroid Impact

From: RSchatte@aol.com
Date: Wed, 26 Nov 1997 21:35:43 -0500 (EST)
Fwd Date: Thu, 27 Nov 1997 08:01:01 -0500
Subject: Scientists Describe Asteroid Impact
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Subj: Scientists Describe Asteroid Impact
Date: 97-11-26 13:11:08 EST
From: AOL News
Scientists Describe Asteroid Impact
.c The Associated Press
By PETER JAMES SPIELMANN
SYDNEY, Australia (AP) - An asteroid that tumbled through space for eons
blasted into the sea off Antarctica more than 2 million years ago with the
force of ``a cosmic bomb,'' a multinational team of scientists said in a
research paper published Wednesday.
Striking the Bellingshausen Sea with the explosive power of 100 billion tons
of TNT, the asteroid Eltanin blew a column of water 3 miles high and punched
a temporary ``oceanic crater'' in the sea, according to the paper, which
appeared in the British science journal Nature.
The researchers estimate the asteroid was at least six-tenths of a mile and
possibly up to 2 1/2 miles in diameter.
The blast in the ocean did not leave a crater on the seabed, but a similar
strike on land would have left a hole 9 to 25 miles across.
Eltanin, the only asteroid ever known to have hit water, triggered waves 65
to 130 feet high, ``devastating mega-tsunamis'' that swamped the coasts of
South America and Antarctica.
``The tsunami ... destroys enormous, large areas. ... In the Pacific Rim
there are signs of such things,'' one of the lead researchers, Rainer
Gersonde of the Alfred Wegener Institute for Polar and Marine Research in
Bremerhaven, Germany, told The Associated Press in a telephone interview
Wednesday.
Sediment spread up to 2,500 miles away and dust, vapor and salts wafted
around the world. Enough debris and hot vapors were emitted to possibly
damage the Earth's ozone layer, the researchers said.
``The dust and vapor probably caused a major change in climate, but whether
that persisted or was for just a few years, we just don't know,'' said
Karsten Gohl, a geologist from Macquarie University in Sydney who worked on
the project.
There is no evidence that the climatic change caused the extinction of any
species.
New seismic and deep-sea surveys conducted in 1995 by the German research
ship Polarstern enabled the scientists to accurately date the blast to the
late Pliocene period, 2.15 million years ago, and to gauge its effects.
The blast was well after the Northern Hemisphere's Ice Age began but ``close
to one of the strongest cooling events in this time period,'' the
researchers' paper said.
``It might be that this strong cooling was related to the impact,'' Gersonde
told the AP.
The fallout from the blast may explain the ``Sirius enigma,'' the puzzle of
why marine fossils are found high above sea level in the Transantarctic
Mountains.
The researchers believe fallout from the steam and vapor cloud dropped
micro-fossils directly on the mountains, an idea that geologist Peter Barrett
at Victoria University of Wellington, New Zealand, called ``reasonably
plausible.''
David Harwood at the University of Nebraska, an expert on the Sirius fossils,
conceded that the fallout theory ``has potential'' but said some Sirius
deposits do not fit the model. He is among those who think moving ice sheets
may have scoured fossil deposits and redeposited them in unexpected sites.
The Eltanin impact was a medium blast, as asteroids go.
About 65 million years ago, a 6-mile-wide asteroid crashed into an area near
Mexico's Yucatan Peninsula, creating a 112-mile-wide crater. Some scientists
believe this event kicked up enough dust to blot out the sun, killing more
than 80 percent of all animals on Earth and leading to the extinction of the
dinosaurs.
But rocks far smaller than Eltanin can cause massive damage: A meteorite only
150 feet across created Arizona's Meteor Crater, 4,000 feet wide and 600 feet
deep. A rock just 30 feet across, hitting Earth from outer space, releases
energy equal to about five Hiroshima-sized bombs.
Although the Earth's surface is 70 percent water, Eltanin is the only
asteroid to strike the ocean that scientists know about, compared with about
140 known to have hit land, Jan Smits of the Research School of Sedimentary
Geology at Amsterdam's Vrije University noted in a commentary on the research
in Nature.
``Where might the traces of these events be hiding?'' Smits asked.
Besides Gersonde, in Germany, researchers on the project included Frank Kyte
at the Institute of Geophysics and Planetary Physics at UCLA and scientists
from the Department of Geology at the University of Salamanca in Spain;
Macquarie University's School of Earth Sciences in Sydney; and the U.S. Naval
Research Lab in Washington.
Eltanin is named for the U.S. research ship that brought up deep sea samples
in 1965 that later were found to contain iridium, an element in asteroids.
AP-NY-11-26-97 1307EST
Copyright 1997 The Associated Press. The information contained
in the AP news report may not be published, broadcast, rewritten
or otherwise distributed without prior written authority of The
Associated Press.